Hi,
Trying to extract a map (package maps) to a shapefile, IIUC the procedure
is to get it into a SpatialPolygonsDataFrame and then use
writePolyShape(). This seems to require an intermediate step through
SpatialPolygons. However, I'm running into some problems:
R> canada <- map("world2Hires", "Canada", plot=FALSE)
R> canada_sp <- map2SpatialPolygons(canada, IDs=canada$names,
+ proj4string=CRS("+proj=longlat
+ellps=wgs84"))
Error in map2SpatialPolygons(canada, IDs = canada$names, proj4string =
CRS("+proj=longlat +ellps=wgs84")) :
map and IDs differ in length
How can these two components be lined up?
I would also appreciate some suggestions on how to write a projection file
for the shapefile. I can see this has been discussed in the past, but at
that time there was no solution.
Cheers,
--
Seb
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